The overall objective of the Mouse Core is to provide for the maintenance of the genotoxicant reporter mouse colonies that will be used by the Projects for their experiments. The Mouse Core will maintain the mouse colonies that will be used by the projects for their experiments. The Mouse Core will maintain the mouse colonies, carry out breeding programs for the production of experimental animals in coordination with each project leader, obtain samples for genotyping during the first week after birth, and cull the unwanted animals before weaning in order to minimize the size and cost of maintaining each line. The Mouse Core will closely monitor the health of the animals and look for the presence of abnormal phenotypes such as the presence of tumors. Extensive recordkeeping will be kept on spread sheets for each line sot that pedigree can be established when indicated. Periodic status reports will be provided to Project leaders. Routine and simple experimental procedures that can be done in the procedural room adjacent to the animal room will be performed by Mouse Core personnel. Routine necropsy and preservation of tissue will be performed by Mouse Core personnel in coordination with Project leaders and other Cores.